Diversity and biological activities of the bacterial community associated with the marine sponge P horbas tenacior ( P orifera, D emospongiae)

The diversity of the cultivable microbiota of the marine sponge P horbas tenacior frequently found in the M editerranean S ea was investigated, and its potential as a source of antimicrobial, antioxidant and antiplasmodial compounds was evaluated. The cultivable bacterial community was studied by isolation, cultivation and 16 S r RNA gene sequencing. Twenty‐three bacterial strains were isolated and identified in the P roteobacteria (α or γ classes) and A ctinobacteria phyla. Furthermore, three different bacterial morphotypes localized extracellularly within the sponge tissues were revealed by microscopic observations. Bacterial strains were assigned to seven different genera, namely V ibrio, P hotobacterium, S hewanella, P seudomonas, R uegeria, P seudovibrio and C itricoccus . The strains affiliated to the same genus were differentiated according to their genetic dissimilarities using random amplified polymorphic DNA ( RAPD ) analyses. Eleven bacterial strains were selected for evaluation of their bioactivities. Three isolates P seudovibrio P1Ma4, Vibrio P1MaNal1 and Citricoccus P1S7 revealed antimicrobial activity; C itricoccus P1S7 and V ibrio P1MaNal1 isolates also exhibited antiplasmodial activity, while two V ibrio isolates P1Ma8 and P1Ma5 displayed antioxidant activity. These data confirmed the importance of P roteobacteria and A ctinobacteria associated with marine sponges as a reservoir of bioactive compounds. Significance and Impact of the Study This study presents the first report on the diversity of the cultivable bacteria associated with the marine sponge P horbas tenacior , frequently found in the M editerranean S ea. Evaluation of the antiplasmodial, antimicrobial and antioxidant activities of the isolates has been investigated and allowed to select bacterial strains, confirming the importance of P roteobacteria and A ctinobacteria as sources of bioactive compounds.